1. Field of the Invention
The embodiments of the present invention relate to the field of nanocomputing.
2. Prior Art
Embodiments of the present invention are intended to produce logic devices that are smaller, faster, less expensive, and more power efficient than anticipated 16 nm CMOS devices. Presently such goals are pursued by dimensional scaling (reducing gate length, operating voltage) and have improved transistor performance for multiple generations. However, as critical device dimensions approach atomic length scales, it will not be possible to reduce critical dimensions further, and alternative means of storing and manipulating information must be found.
Conventional computing devices including CMOS devices associate computational state (information) with electronic charge and then manipulate, store and detect those charges to perform logic operations. However, computational state can be associated with other physically conserved quantities including spin. Many concepts have been published which involve using the spins of single electrons in quantum dots (see “Granular nanoelectronics”, Bandyopadhyay et al., IEEE Potentials, April/May 1996, Pgs. 8–11 and “Self-assembled nanoelectronic quantum computer based on the Rashba effect in quantum dots”, Bandyopadhyay, Physical Review B, The American Physical Society, Vol. 61, No. 20, May 15, 2000, Pgs. 813–820) to encode information. The disadvantages of this computing paradigm include a basic trade off between the tight coupling between spins and the resulting higher decoherence rate as well as a lack of logic architecture which would ensure input isolation.
Several different implementations of QCA systems have been proposed that utilize different physical invariants to store information and different interaction mechanisms One such implementation uses electric dipoles stored in quantum dots to store information and the electrostatic force field to effect the interaction (see “A Device Architecture for Computing with Quantum Dots”, Lent et al., Proceedings of the IEEE, Vol. 85, No. 4, April 1997, Pgs. 541–557). This approach suffers from several problems including sensitivity to stray charge, system hang up in metastable states, asynchronous operation and others.
Another implementation uses magnetic dipoles to store information and the magnetic coupling between adjacent dipoles to enable cell interaction. The sequential flipping of magnetic configurations in a QCA architecture can be used to perform logic operations and several simple logic gates have been described in the literature (see “Nanocomputing by field coupled nanomagnets”, Casba et al., IEEE Transactions of Nanotechnology, Vol. 1, No. 4, 2002). These implementations involve discrete magnetic domains and discrete electric dipole moments.